Research Highlights: Perovskites
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RESEARCH HIGHLIGHTS :
Perovskites
By Pabitra K. Nayak
Metal halide perovskite materials have revolutionized low-cost processed optoelectronic devices. Efficiency records of perovskitebased devices break at a regular pace. Fundamental understanding of this class of materials is progressing rapidly, leading to better optimization and stability. MRS Bulletin presents coverage of the most recent impactful advances in the burgeoning field of perovskite research.
H
igh-efficiency halide perovskitebased optoelectronic devices are mostly comprised of polycrystalline thin films. However, single-crystal materials show better charge-carrier transport, lower density of defects, and better stability in comparison to their polycrystalline counterparts. However, fabrication and mass production of large area devices with single-crystal thin films has been a challenge. Sheng Xu from the University of California, San Diego, and co-workers have reported in Nature (doi:10.1038/ s41586-020-2526-z) a solution-based lithography-assisted epitaxial growth and transfer method that enables fabrication of single-crystal perovskites
L
ong-term stability of halide perovskite solar cells has been a major concern and comes in the way of commercial deployment of the technology. Yen-Hung Lin and Henry Snaith from the University of Oxford and co-workers have found a way to address this stability issue. In work published in Science (doi:10.1126/ science.aba1628), they showed that by incorporating the ionic compound 1-butyl-1-methyl-piperidinium tetrafluoroborate in a formamidinium-cesium lead-trihalide perovskite material, they could achieve highly stable perovskite solar cells. Under simulated sunlight and
on any arbitrary substrate. The authors describe precise control of the thickness (from 600 nm to about 100 µm) and area (continuous thin films up to about 5.5 cm × 5.5 cm), and compositional gradient in the thickness direction of the single-crystal thin films. These solution-grown and -transferred perovskite single1 cm crystal films have quality comparable to those directly grown on epitaxial substrates and were An array of single-crystal-based flexible perovskite solar Inset: a cross-sectional scanning electron microfound to be mechanically flex- cells. scope image of the cell. Credit: Nature. ible. The authors also prepared lead-tin gradient alloying to achieve a graded electronic bandgap. perovskite single crystal show better stabilOptoelectronic devices based on the ity than their polycrystalline counterparts. ambient atmosphere, the encapsulated cells retained 95% of the post-burn-in efficiency (the stabilized efficiency after the initial drop in efficiency that happens in a short timespan) after a period of 1200 hours at 85°C. The perovskite material used in this work has a mixed-halide composition, which makes it susceptible to light-induced halide segregation, another challenge associated with this class of materials. The authors have reported that the ionic compound additive slows down the compositional segregation in the perovs
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